1. Field of the Invention
This invention relates to a composition comprising beta-1,4 glucan particles, more specifically food grade attrited non-derivatized microcrystalline cellulose (MCC) particles, at least partially coated or occluded by a food grade barrier dispersant comprising a calcium/sodium alginate salt complex. The barrier dispersant permits dry attrited MCC particles to be formed without agglomeration and subsequently redispersed to a colloidal type suspension in aqueous media. The invention also relates to processes for the manufacture of the composition, and methods for its use.
2. Statement of Related Art
Microcrystalline cellulose (MCC) comprises the tiny rodlike microcrystals of partially hydrolyzed cellulose (beta-1,4 glucan). Colloidal MCC is employed as a bodying agent and a retardant of crystal growth in frozen desserts. In oil-in-water emulsions, the MCC solid particles coat the oil droplets and also thicken the aqueous phase. Another use for colloidal MCC is as a foam stabilizer in aerated food systems. [see Food Theory and Applications, Paul & Palmer, Chapter 4, p. 199 "Starch and Other Polysaccharides" by E. Osman, Wiley & Sons, N.Y. (pub) 1972].
The beta-1,4 glucan may be derived from any desired chemical degradation method applied to a selected cellulose material. Upon completion of the desired degradation, the residue is collected as a filter cake and is thoroughly washed to remove insoluble impurities. The washed cake, preferably containing about 40% solids, is then subjected to mechanical disintegration. In the chemical degradation treatment and subsequent washing, microcrystalline cellulose is freed by cleaving the cellulose chains in the amorphous regions. The individual crystallites then must be separated or peeled from the treated fiber or fragment. During the disintegration newly created surfaces are formed as the microcrystals are separated from the degraded material, and unless the individual microcrystals are maintained in a separated condition they will re-bond. In order to obtain efficient shearing, the solids content of the mass being subjected to disintegration should be sufficiently high to provide an efficient transfer of the shear forces. On the other hand, the solids content should not be so high as to allow the separated micro-crystals to coalesce and form large aggregates owing to insufficient water present to hydrate with the newly created surfaces of the microcrystals.
The mechanical attrition may be effected by the use of various standard equipment such as kitchen mixers, planetary mixers, ball mills, attrition mills, high-speed shearing devices such as a Waring blender, and the like. Additionally, the residue of the hydrolysis treatment preferably in the presence of an aqueous medium, may be subjected to a shearing action and to a rubbing action between the particles by forcing the mixture of residue and aqueous medium through passages of limited cross-section such as found in perforated plates. The attrition should be sufficient to produce a mass wherein at least about 1% by weight and preferably at least 30% by weight of the particles have an average length not greater than 1.0 micron as determined by electron microscopic examination. Some of the particles in such a mass may have a length or maximum dimension as low as a few hundredths of a micron.
It is desirable to dry the attrited material in order to achieve efficiencies of storage and shipping. However the dried product becomes hornified, probably due to agglomeration of numbers of smaller particles that become bonded together by hydrogen bonding forces during drying. These forces are second in strength only to primary valence bonds and accordingly, when the dried product is to be redistributed in an aqueous medium, substantial amounts of energy are required to break the hydrogen bonds.
In order to break this hydrogen bonding, U.S. Pat. No. 3,539,365 - Durand, et al. suggests coating the beta-1,4glucan particles with a barrier material and the patent mentions a variety of materials useful for this purpose and indicates sodium carboxymethylcellulose (CMC) as being the most effective. This patent states (at column 5) that methylcellulose, hydroxypropyl methylcellulose, guar gum, alginates, sugars, surfactants and other hydrocolloids may have a slight barrier action when added in appreciably higher proportions. Sodium carboxymethylcellulose is not universally acceptable in food products.
U.S. Pat. No. 4,263,334 - McGinley, recognizing the same problem, avoids the use of CMC by teaching a combination of additives consisting of a first ingredient which is a carbohydrate sweetener such as sucrose, dextrose, or hydrolyzed cereal solids and a second ingredient which is a hydrocolloid gum such as guar gum, locust bean gum, gum arabic, sodium alginate, propylene glycol alginate, carrageenan, gum karaya, or xanthan gum.
U.S. Pat. No. 3,573,058 - Tiemstra discloses compositions of attrited MCC admixed with various hydrocolloids and then co-dried by various methods including spray drying. Sodium alginate and propylene glycol alginate are disclosed as useful hydrocolloids, among many others. It is asserted that the compositions permit dry storage and rehydration without the need for additional attrition after drying.
U.S. Pat. No. 4,311,717 - McGinley discloses a stabilizing agent for dry mix food products which consists of MCC, sodium carboxymethylcellulose, and whey or milk solids. In this instance, the sodium carboxymethylcellulose combined with the whey or milk solids acts as a barrier between the dry cellulose particles, functioning as a barrier dispersant.
U.S. Pat. No. 4,980,193 - Tuason, et al. discloses a cellulose based stabilizer system consisting of attrited cellulose, starch, a non-thickening water-soluble diluent such as maltodextrin, and whey or non-fat dry milk.
Alginates: Alginic acid is identified in The Merck Index, 9th ed. , Merck & Co. , Rahway, N.J. (pub.) 1976 at no. 230 as a hydrophilic, colloidal polysaccharide obtained from seaweed which is very slightly soluble in water. When it is in the form of its sodium salt, however, it becomes readily soluble in water, forming a viscous colloidal solution [see The Merck Index, above, at no. 229]. According to Merck, sodium alginate has known uses in the manufacture of ice cream where it serves as a stabilizing colloid; in drilling muds; in coatings; in the flocculation of solids in water treatment; as a sizing agent; thickener; emulsion stabilizer; suspending agent in soft drinks; in dental impression preparations; and in pharmaceutical preparations as a suspending agent. The conversion of water-soluble sodium alginate to water-insoluble calcium alginate by the addition of a calcium salt is known. While the thickening properties of alginate salts generally are well known, it is important to distinguish between the use of alginates as barrier dispersants for a dry product which will be added to water and the use of alginates in existing aqueous systems.
The gelation of algin polymers with polyvalent cations, and in particular with calcium, is well known and is discussed in Gum Technology in the Food Industry by Glicksman, Academic Press, N. Y. (1969) at 245-246 and in the Handbook of Water-Soluble Gums and Resins, Chapter 2 - Alginates by Cottrell & Kovacs, McGraw-Hill Book Co., N.Y. (1980), at 2-10 through 2-15.
U.S. Pat. No. 3,012,892 - Marcus discloses the precipitation of alginic acid from sodium alginate by the addition of an alginate solution to acidic calcium chloride solution whose pH is 4 or less.
U.S. Pat. No. 5,082,684 - Fung discloses the cross-linking of sodium alginate with calcium salts, including calcium chloride.
U.S. Pat. No. 3,060,032 - Glicksman discloses gelling sodium alginate with tricalcium phosphate, dicalcium phosphate, calcium carbonate, calcium tartrate, or calcium sulfate, with the control of gelling by the use of a retarding agent such as sodium hexametaphosphate, trisodium phosphate, tetrasodium pyrophosphate, sodium tetraphosphate, sodium tripolyphosphate, or a calcium complexing agent such as sodium carbonate or sodium citrate. The calcium salt is employed at a level of 10 to 50, preferably 25 % by weight of the algin.
U.S. Pat. Nos. 4,216,242 and 4,264,637 - Braverman disclose the use of alginates as stabilizers in combination with MCC in aqueous freezable gel compositions which also may contain starch and/or xanthan gum and/or sodium carboxymethylcellulose. Both of these patents state that calcium tends to form non-reversible gels with alginates.
U.S. Pat. No. 4,192,900 - Cheng discloses in its description of the prior art that it is known that sodium alginate becomes a viscous mass when dissolved in water and is capable of solidification by calcium chloride, citing to U.S. Pat. Nos. 2,403,547 and 3,093,483. This patent discloses mixing starch with a gelling hydrocolloid (preferably sodium alginate) and/or methylcellulose and, where the hydrocolloid is sodium alginate, gelling it by contacting it with calcium ions (particularly calcium chloride), followed by drying of the particles.
U.S. Pat. No. 4,624,856 - Vanderveer, et al., discloses addition of a calcium source to a sodium alginate to form a gel which is capable of being ground.